Multiphase thermal arc jet



July 7, 1964 R. M. SPONGBERG 3,140,421

MULTIPHASE THERMAL ARC JET Filed April 17, 1962 2 2 Sheets-Sheet l G95504 f Y 25 F L E 2 JNVENTOR e/c/mea M. s wastes BY W y 7, 1964 R. M.SPONGBERG 3,140,421

MULTIPHASE THERMAL ARC JET Filed April 1?, 1962 2 Sheets-Sheet 2 UnitedStates Patent Ofifice 3,146,421 Patented July 7., 1964 3,140,421MULTIPHASE Tl-ERMAL ARC JET Richard M. Spongherg, 6507 Lucas Ave.,Oakland 11, Calif. Filed Apr. 17, 1962, Ser. No. 188,284 Claims. (Cl.315-111) (Granted under Title 35, US. Code (1952), sec. 266) Theinvention described herein may be manufactured and used by or for theUnited States Government for governmental purposes without payment to meof any royalty thereon.

This invention relates to a thermal arc jet device for creating a highenthalpy gas by the transfer of power to the gas from a multiphaseelectrical power source.

One object of the invention is to provide a thermal arc jet device whichavoids local heating and the subsequent deterioration of the electrodes.

Another object is to provide a thermal arc jet device which permits highcurrent densities and in which there is a minimum of heat transfer tothe electrodes.

A further object is to provide a thermal arc jet device wherein the arctravels in line with the gas thus providing a large heat transfer to thegas.

A still further object is to provide a multiphase thermal arc jet withan electrode arrangement wherein the arc occurs only between adjacentelectrodes without bridging an intermediate electrode.

These and other objects will be more fully understood from the followingdetailed description taken With the drawing wherein:

FIG. 1 shows a partially cutaway end view of a thermal arc jet accordingto the invention;

FIG. 2 shows a sectional view of the device of FIG. 1 along the line2--2;

- FIG. 3 shows a modification of the device of FIGS. 1 and 2 usingdiffusion of the gas past a pin electrode in a multiphase system; and,

FIG. 4 shows a modification of the pin electrode'of FIG. 3.

A thermal arc jet is a device which transfers electrical energy to agas. Positive and negative ions are accelerated between the electrodesand collide with neutral gas molecules thus imparting momentum andenergy to these neutral particles and also provide additional ionizationof the gas. According to this invention, a plurality of annularelectrodes separated by insulating spacers are connected to a highfrequency multiphase power source with the first and last electrodesconnected in-phase so that a new are will strike between the first twoelectrodes following the striking of an are between the last twoelectrodes. The use of a high frequency multiphase system is superior toD.C. systems of this type because the arcs are periodic instead ofcontinuous and thus increase electrode life. Also, the heat transfer tothe gas is more efficient.

In one embodiment of the invention, a D.C. arc is used to providepreionization of the gas.

Referring more particularly to the drawing, FIGS. 1 and 2 show amultiphase thermal arc jet having'a plurality of annular shapedelectrodes 11, 12, 13 and 14 separated by insulator spacers 15, 16 and17. In one device built, the spacers were made of Teflon but otherinsulating materials may also be used.

The electrodes 11, 12, 13 and 14 are made of a heat resistant conductivematerial such as. tungsten. However, in some systems, it is possible touse copper electrodes or electrodes of other conducting materials.Cooling jackets 18 and 19 surround electrodes 12 and 13. These may bemade of copper or other conducting material for supplying power toelectrodes 12 and 13. Coolant material is supplied to channels 22 inmembers 12, 13, 18 and 19 through the coolant supply tubes 23 and 24which may also be used as electrical leads. Heat and electricalconducting members 20 and 21 surround electrodes 11 and 14. Coolingmeans may also be provided for electrodes 11 and 14, if desired, thoughthis, in some cases, is not needed.

A gas supply tube 25 supplies gas along the tangent of chamber 26 inmember 20 from gas supply 27, as shown in FIG. 1. An expansion nozzle 28is connected to the electrode assembly at the opposite end from member20. The electrode assembly and nozzle are held in sealed relation bymeans of a frame 29 made up of end plates 30 and 31 which are secured bytie rods 33 and nuts 34. The frame 29, member 20, nozzle 28 and member21, act as the power lead for electrodes 11 and 14. Multiphase currentis supplied to the electrodes 11, 12, 13 and 14 by means of tubes 23 and24, end plates 30, 31, and tie rods 33 from a multiphase supply 35 shownschematically as a three-phase supply in FIG. 2. The electrodes 11 and14 are connected in-phase so that a new are discharge between electrodes11 and 12 follows the discharge between electrodes 13 and 14. Insulators15, 16 and 17 have annular recessed portions 39, 40 and 41 to reduceheating of the insulators and to prevent breakdown across the surface ofthe insulators.

In the operation of the device, a three-phase power supply is connectedto the electrodes 11, 12, 13 and 14 as described above. A gas such asair, hydrogen, helium, nitrogen or argon is introduced from supplysource 27 through supply tube 25 tangentially into chamber 26 in member20 and then travels down the discharge cavity 36 with a vortex motionpast electrodes 11, 12, 13 and 14 through the constriction 32 into theexpansion nozzle 28. As the gas flows down the tube, are discharges areset up first between electrodes 11 and 12, then 12 and 13 and, in turn,electrodes 13 and 14, and then back again to electrodes 11 and 12. Thearc discharge column is parallel to the gas flow so that the arc travelsin line with the gas which allows for greater heat transfer to occur.The swirl added to the gas causes the arc to be constricted to a smallcolumn in the center of the electrodes to allow high current densitiesand high enthalpy levels to be achieved in the device and, also tomaintain a cooler gas sheath close to the electrodes which reduces heattransfer to the electrodes. The gas enters the constriction 32 in nozzle28 at sonic or greater velocity and is expanded to higher velocities inthe nozzle 28.

In the device of FIG. 3 the annular electrodes 51, 52, 53 and 54 aresubstantially the same as the annular electrodes in FIGS. 1 and 2.Cooling jackets 55, 56, 57 and 58 are provided for each of theseelectrodes. A nonconducting cooling material such as air is supplied tothe cooling jackets 55, 56, 57 and 58 from supply 60 through aninsulating tube 61 made of a material such as rubber' and through tubes62a, 63a, 64a and 65a. The coolant discharge tubes 62b, 63b, 64b and 65bare made of conducting material and act as leads for electrodes 51, 52,53 and 54 from the multiphase power supply 67, which is shown as athree-phase supply, though more phase and additional annular electrodesmay be used, if desired. The electrodes 51, 52, 53 and 54 are separatedby insulator spacers 69, 70, 71 and 72 as in FIGS. 1 and 2. Theelectrodes and spacers provide a central cavity 73 for the passage ofgas to be heated as in FIGS. 1 and 2. The gas to be heated is suppliedto the tube from gas supply 74 through tube 75 to a chamber 76 as inFIGS. 1 and 2. A direct current supply 77 is connected between pinelectrode 78 and an additional annular electrode 79 and causesionization of the gas which is diffused past the pin electrode '78 inspace 80. The gas diffusing past the pin electrode acts to cool the pinelectrode. The ionized gas u entering the discharge space betweenelectrodes 51 and 52 permits breakdown between these electrodes at lowervoltages and thus provides greater heating of the gas.

A plenum or mixing chamber 82 is provided between the electrode systemand a nozzle 83. so that the heat of the gas entering the constriction84 is substantially uniform. Th coolant from supply 60 is supplied tothe cooling space 85 in member 86 surrounding the mixing chamber and tospace 87 in nozzle member 88 through tubes 91a and 92a. The coolingspaces 85 and 87 are provided with discharge tubes 91b and 92b. Coolingmay be provided for the members 93 and 79 in a similar manner, ifdesired.

The operation of the device of FIG. 3'is similar to the device of FIGS.1 and 2. Gas from supply 74 enters the chamber 76 with a vortex motion.The gas diffuses past the pin electrode 78 and annular electrode 79wherein it is ionized. It then passes through the tube cavity 73 to themixing chamber 82. Because of the three-phase power supply connected tothese electrodes, a discharge is first started between electrodes 51 and52, then between electrodes 52 and 53, and then between electrodes 53and 54. This adds heat energy to the gas so that a high energy gasenters the mixing chamber 82. This high energy gas is then expanded to ahigh velocity in the expansion nozzle 83. After the discharge betweenelectrodes 53 and 54 the next discharge will be between electrodes 51and 52 since electrodes 51 and 54 are connected in-phase.

In FIG. 4, a modification of the pin electrode 78 of FIG. 3 is shown.The pin electrode 78a has a tungsten tip 98 to provide a longer life forthe pin electrode. A channel 99 is provided as a path for escape of thegas that builds up behind the tungsten tip 98 during the manufacture ofthe device. The tip may be made porous so that additional gas fromsupply 74 may be supplied through channel 99 to aid in cooling the tip.The electrodes 51, 52, 53 and 54 may also be made porous so thatadditional gas may be supplied to the cavity 73 through the electrodeswhich will aid in cooling the electrodes.

While a separate coolant supply has been shown, in some cases the gasfrom the supply source can be used as the cooling material such as whenthe porous electrodes are used. Also, a heat exchanger may be providedsurrounding the electrode system for adding heat to the supply gas.

Also, various means may be used to provide the vortex motion for the gassuch as a spiral plate adjacent the chambers 26 and 76. The electrodesare made to project toward the central cavity in the center to increasethe effective length of the conductor and to aid in removing theinsulators from the discharge path. The systems have been shown with asingle A.C. supply but as the D.C. supply is not electrically connectedoutside the tube to the A.C. supply, so also more than one multiphaseA.C. system connected to separate electrodes in the same gas flow pathcould be used. For example, four additional electrodes could be locatedbetween electrode 54 and the mixing chamber 82 and these could beconnected to a separate three-phase A.C. supply to add more energy tothe gas.

There is thus provided a multiphase thermal arc jet for creating highenthalpy gas. It is obvious that there may be other uses for the devicethan that disclosed.

While certain specific embodiments have been described in detail, it isobvious that numerous changes may be made without departing from thegeneral principle and scope of the invention.

I claim:

1. A multiphase thermal arc jet device, comprising: an electrode systemincluding four annular electrodes of heat resistant material, an annularelectrical insulator spacer between each pair of electrodes to therebyprovide a plurality of discharge spaces within said electrode system, acooling jacket surrounding the two intermediate electrodes, means forsupplying a coolant to said cooling jackets, a conductive cup-shapedmember surrounding one of the other of said four electrodes, a cavity insaid cup-shaped member adjacent said one of the other electrodes, meansfor supplying a gas along the tangent of said cavity to thereby give thegas a vortex motion within said electrode system, a conductive expansionnozzle at the end of said electrode system remote from said cavity inelectrical engagement with the remaining one of said four electrodes, afirst conductive plate member at one end of said electrode system inelectrical engagement with said cup-shaped member, a second conductiveplate member at the other end of said electrode system in electricalengagement with said nozzle, conductive means connected between saidfirst and second plate members, a three-phase power supply, meansincluding said means connected between said plate members for connectingone phase of said power supply to said first and said second platemembers and means for connecting the other two phases of said powersupply to said two intermediate electrodes.

2. A multiphase thermal arc jet device, comprising: an electrode systemincluding a plurality of annular electrodes, means for cooling saidannular electrodes, an annular electrical insulator spacer between eachpair of electrodes to thereby provide a plurality of discharge spaces, amultiphase power supply, means for connecting two non-adjacent annularelectrodes to one phase of said power supply, means for connecting theannular electrodes intermediate said two annular electrodes to the otherphases of said power supply, means for supplying gas with a vortexmotion at one end of said electrode system into said discharge spaces,an expansion nozzle at the end of said electrode system remote from saidgas supply means and a mixing chamber between said electrode system andsaid expansion nozzle.

3. A multiphase thermal arc jet device, comprising: an electrode systemincluding a plurality of annular electrodes of heat resistant material,means for cooling said annular electrodes, an annular electricalinsulator spacer between each pair of electrodes to thereby provide aplurality of discharge spaces, a multiphase power supply, means forconnecting two nonadjacent annular electrodes to one phase of said powersupply, means for connecting the annular electrodes intermediate saidtwo annular electrodes to the other phases of said power supply, a pinelectrode at one end of said electrode system, a direct current supply,means for connecting said direct current supply between said pinelectrode and one of said annular electrodes adjacent said pinelectrode, a chamber adjacent and surrounding a portion of said pinelectrode, means for supplying gas with a vortex motion tangential tosaid chamber past said pin electrode into said discharge spaces, anexpansion nozzle at the end of said electrode system remote from saidpin electrode and a mixing chamber between said electrode system andsaid expansion nozzle.

4. A multiphase thermal arc jet device, comprising: an electrode systemincluding a plurality of annular electrodes of heat resistant materialhaving inwardly directly projecting surfaces; an annular electricalinsulator spacer between each pair of electrodes to thereby provide aplurality of discharge spaces; said insulator spacers having inwardlydirectly concave surfaces; a multiphase power supply; means forconnecting two nonadjacent annular electrodes to one phase of said powersupply; means for connecting the annular electrodes intermediate saidtwo annular electrodes to the other phases of said power supply; a pinelectrode, having a conical tip, at one end of said electrode system; apin support member surrounding said pin electrode; an annular member,having a conical opening therein, adjacent said pin electrode; said pinelectrode having its conical tip projecting into said conical opening; adirect current supply; means for connecting said direct current supplybetween said pin electrode and one of said annular electrodes adjacentsaid pin electrode; means for supplying gas with a vortex motion pastsaid pin electrode into said discharge spaces; an expansion nozzle atthe end of said electrode system remote from said pin electrode; amixing chamber between said electrode system and said expansion nozzleand means for cooling said annular electrodes, said nozzle and saidmixing chamber.

5. A multiphase thermal arc jet device, comprising: an electrode systemincluding a plurality of annular electrodes of heat resistant materialhaving inwardly directly projecting surfaces; an annular electricalinsulator spacer between each pair of electrodes to thereby provide aplurality of discharge spaces; said insulator spacers having inwardlydirectly concave surfaces; a multiphase power supply; means forconnecting two nonadjacent annular electrodes to one phase of said powersupply; means for connecting the annular electrodes intermediate saidtwo annular electrodes to the other phases of said power supply; acooling jacket surrounding each of the annular electrodes connected tosaid multiphase power supply; said annular electrodes and saidsurrounding cooling jackets having annular cooling chambers; means forsupplying a coolant to said annular cooling chambers; a pin electrode,

having a conical tip, at one end of said electrode system; a pin suppontmember surrounding said pin electrode; and annular member, having aconical opening therein, adjacent said pin electrode; said pin electrodehaving its conical tip projecting into said conical opening; a directcurrent supply; means for connecting said direct current supply betweensaid pin electrode and one of said annular electrodes adjacent said pinelectrode; means for supplying gas with a vontex motion past said pinelectrode into said discharge spaces; an expansion nozzle member at theend of said electrode system remote from said pin electrode; a mixingchamber member between said electrode system and said expansion nozzle,said nozzle member and said mixing chamber member having annular coolingchannels therein; and means for supplying a coolant to said channels insaid nozzle member and said chamber member.

References Cited in the file of this patent UNITED STATES PATENTS I2,964,479 Schneider et al. Dec. 13, 1960 2,964,678 Reid Dec. 13, 19603,048,736 Emmerich Aug. 7, 1962

1. A MULTIPHASE THERMAL ARC JET DEVICE, COMPRISING: AN ELECTRODE SYSTEMINCLUDING FOUR ANNULAR ELECTRODES OF HEAT RESISTANT MATERIAL, AN ANNULARELECTRICAL INSULATOR SPACER BETWEEN EACH PAIR OF ELECTRODES TO THEREBYPROVIDE A PLURALITY OF DISCHARGE SPACES WITHIN SAID ELECTRODE SYSTEM, ACOOLING JACKET SURROUNDING THE TWO INTERMEDIATE ELECTRODES, MEANS FORSUPPLYING A COOLANT TO SAID COOLING JACKETS, A CONDUCTIVE CUP-SHAPEDMEMBER SURROUNDING ONE OF THE OTHER OF SAID FOUR ELECTRODES, A CAVITY INSAID CUP-SHAPED MEMBER ADJACENT SAID ONE OF THE OTHER ELECTRODES, MEANSFOR SUPPLYING A GAS ALONG THE TANGENT OF SAID CAVITY TO THEREBY GIVE THEGAS A VORTEX MOTION WITHIN SAID ELECTRODE SYSTEM, A CONDUCTIVE EXPANSIONNOZZLE AT THE END OF SAID ELECTRODE SYSTEM REMOTE FROM SAID CAVITY INELECTRICAL ENGAGEMENT WITH THE REMAINING ONE OF SAID FOUR ELECTRODES, AFIRST CONDUCTIVE PLATE MEMBER AT ONE END OF SAID ELECTRODE SYSTEM INELECTRICAL ENGAGEMENT WITH SAID CUP-SHAPED MEMBER, A SECOND CONDUCTIVEPLATE MEMBER AT THE OTHER END OF SAID ELECTRODE SYSTEM IN ELECTRICALENGAGEMENT WITH SAID NOZZLE, CONDUCTIVE MEANS CONNECTED BETWEEN SAIDFIRST AND SECOND PLATE MEMBERS, A THREE-PHASE POWER SUPPLY, MEANSINCLUDING SAID MEANS CONNECTED BETWEEN SAID PLATE MEMBERS FOR CONNECTINGONE PHASE OF SAID POWER SUPPLY TO SAID FIRST AND SAID SECOND PLATEMEMBERS AND MEANS FOR CONNECTING THE OTHER TWO PHASES OF SAID POWERSUPPLY TO SAID TWO INTERMEDIATE ELECTRODES.